From my ship design guide. Once again, please bear in mind that this is just one way it could be done...

Spelljamming HelmThis ornate reclining leather bucket seat, complete with armrests, a head rest, and a cup holder, is quite comfortable to sit in.Wondrous Item
Lv 23 Minor 425,000 gp
Lv 24 Series 525,000 gpProperty: The Minor helm may lift a vessel and its contents with a combined weight of up to 500 tons.
The Major helm may lift a vessel and its contents with a combined weight of up to 1,000 tons.
Each occupied series helm may lift a vessel and its contents with a combined weight of up to 300 tons per series helm.Power (At Will): The Minor helm may fly at a rate of 6 squares per move action. The Major helm may fly at a rate of 12 squares per move action if hauling a load of up to 500 tons, or at a rate of 6 squares if hauling a load of up to 1,000 tons. A Series helm may fly at a rate of 6 squares per move action. For all helms, the occupant(s) merely concentrates to pilot the ship. If the helmsman expends an Encounter power, then the ship gains a speed bonus equal to half the level of the Encounter power. The effects last until the end of the helmsman’s next turn. Series helmsmen must all expend an Encounter power of equal level.Power (At Will): The spelljamming helm may attain spelljamming speed with a base rate of 100 million miles per day (assuming a 10-hour travel period; otherwise, the ship travels at 10 million miles per hour). If the helmsman (or helmsmen in the case of a series helm) expends a Daily power, then the ship gains a speed bonus equal to 10 x ½ Daily power level in millions of miles per day (or ½ Daily power level in millions of miles per hour for each hour the character occupies the helm).Special: The helm may be staffed for up to five hours, at which time the occupant becomes fatigued. A short rest will negate the effects. After ten hours, the occupant becomes exhausted and requires an extended rest before operating the helm again. It takes five minutes for the occupant to attune to the helm, after which he or she may use its powers. All seats must be occupied in order to operate the helm. The helm must be attuned to a vessel via the Bind Helm ritual before it may be used to fly the craft. The helm may serve as a focus item for the Plane Shift ritual.

Description seems at odds with 4e art; shouldn't it be a hard stone throne with spikes and gemstones and such?

Heck no! If I'm going to sit in a chair for hours on end, I want to ride in style!

I thought gold was more valuable in 4e than in previous editions. Price seems rather high, especially given the common complaint about "capture a ship, sell helm (ignore cargo), retire".

I'm not sure about the pricing yet. In my campaign, bound elementals provide the tactical speed while eldritch machines propel a ship to spelljamming speed. Helms are a rare item that none from Eberron have. The Imperial Eladrin Navy doesn't use them either as their "helm" is grown into the ship.

Tons - do you mean actual weight, or SJ "tons"? By weight, that's not very much; a small coaster is about it. By SJ tons, that's a monster of a ship.

By tonnage I do mean weight; actually that is a bit low, the U.S.S. Constitution displaces 2,200 tons.

It only works 10 hours a day? What if you have 2 or more helmsmen working in shifts? Does the ship just drift the other 14 hours a day?

The helm can run 24/7, it's the pilot that can't go more than 10 hours a day.

No variance in speed due to skill of the helmsman?

No, the variance in speed comes from channeling energy into the helm. Encounter powers of the arcane/divine/psionic power source (and possibly others) give you a tactical speed bonus. Channeling a daily power gives you a spelljamming speed bonus. The level of the power determines what bonus you'll get.

In 4th ed, items prices are tied into level
Flying effects in 4th ed are more powerful/rare, hence why I believe they made spelljammers Epic level in the Manual of the Planes but we need it at Paragon level! to let folk play SJ at that level. Very important.
yes, having helms as removable objects of great welth would cause too many problems

my answer:

Minor Helm = lvl 15 item, allowing Paragon characters to use. As you can get items up to +4 levels above you iirc as treasure/rewards.
but shoudl work on all common sizes of ship hulls, tonnage needs ot be less of an issue, because many cargo ships would be big heavy things. and most SJ ships SHOULD be cargo and cargo/semi-warships.
you cna't have pirates outnumbering traders, for instance

Major Helm lvl 30 = Epic level and massive ships.

here is an answer to the way too many helms = too much loot
Once a helm is fixed into a ship by the ritual, if it is ever removed from that ship, the helm becomes a non-magic standard item!
this I also think would be what the Arcane would do: make helms "1 ship items", the customer must come back for more...he can't just keep swapping it about.
ie, keeps them in business, you see?

I have to ask: what kind of a setting do you envision for your 4e spelljammer? That might help you with design decisions. Is it all high magic, where epics only need apply? Or can you find asteroid farmers and such? Is it classical solar systems, or the world-planes of 4e? Etc.

4th edition already has a problem with item value... a level 15 sword is, as silverblade noted, worth just as much as a level 15 spelljamming helm/ship.

but anyways, the other reason item value isn't as much of a problem is that you arbitrarily only get 1/5 the value of the magic item when you sell it (which just seems remarkably stupid to me, but that's the rules)

@night_druid: For my campaign, spelljamming literally took off a scant five years after the first airship took to the skies in Eberron. The Zilargo gnomes, working with House Cannith and House Lyrandar, kept pushing the artifice envelope to see how far and how high they could take an airship, and as more and more problems arose- like a lack of gravity after you move away from a planet, no air up there, harsh temperatures and harsher harmful radiant energy, they kept inventing new rituals to overcome the problems. When it became aparent that other planets were really far away, they created an eldritch machine operated by someone with the Mark of Passage (or a really good skill with Arcana) to attain spelljamming speed. Then the Zilargo Astronomical Society, who perfected spelljamming artifice, went broke.

Once the Five Nations realized how much national prestige they'd get by being the first to do something in new wild space, they licensed the artifice and built their own spelljammers. Each nation has their own unique design; Thrane uses the whaleship, Breland has the battle dolphin, etc. They're basically "Eberronized" versions of the old 2e ships, but with elemental rings. Of course the real reason for the wildspace race isn't national prestige; the nation that controls all the dragonshards up there controls a significant chunk of the dragonshard economy. After all, dragonshards are just unrefined residuum (and that's straight from Keith Baker), and residuum is used in all sorts of ways.

Wildspace and the Astral Sea beyond Shardspace is just waiting to be explored and conquered... unless somebody got there first...

Elvith Jars wrote:@night_druid: For my campaign, spelljamming literally took off a scant five years after the first airship took to the skies in Eberron. The Zilargo gnomes, working with House Cannith and House Lyrandar, kept pushing the artifice envelope to see how far and how high they could take an airship, and as more and more problems arose- like a lack of gravity after you move away from a planet, no air up there, harsh temperatures and harsher harmful radiant energy, they kept inventing new rituals to overcome the problems. When it became aparent that other planets were really far away, they created an eldritch machine operated by someone with the Mark of Passage (or a really good skill with Arcana) to attain spelljamming speed. Then the Zilargo Astronomical Society, who perfected spelljamming artifice, went broke.

I may be getting slightly off topic here, but I just had to say I really like these ideas. Requiring the Mark of Passage for Spelljammer flight is brilliant IMO, and it brings one more player (House Orien) into the picture. Correct me if I'm wrong, but this would mean that a Spelljamming ship in Eberron would require two "pilots" - a Lyrander pilot for tactical speeds (planet side travel and possibly also in battle) and an Orien pilot for spelljamming speeds.

What kind of repercussions do you see happening from those two houses (Lyrander and Orien) working together?

Well the eldritch machine operator doesn't actually steer the ship; he/she just operates the engine Mr. Scott style. It's the helmsman (in this case the Lyrandar pilot) that actually steers. I figure that allure of exploration and cash along with personality screening keeps the House rivalries at bay. Besides, anybody going up there is going to get instant rockstar famous, especially given the newness of spelljamming to Eberron, and looking like team players only helps the Houses.

Important note: For my 4e campaign, I did a reboot of SJ, rather than conversion and tweaks.

Aether Drive
The eldritch machine looks something like the Yamato’s wave motion engine crossed with Star Trek: Enterprise’s warp core, with exhaust pipes sticking out of it like an old WWII piston engine. The exhaust pipes poke out of the hull. Ethereal smoke streams out of the exhaust and leaves a trail.

The machine is powered by dragonshards that are housed in a converter assembly. The converter assembly slowly transforms the dragonshards into residuum and the residuum is then used to create the ethereal substance used for propulsion. The dragonshards require regular replacement. Counter-rotating impellers use the ethereal substance as a working fluid that propels the ship at spelljamming speed.

It takes five people to operate the eldritch machine. The chief machinist gets the best job. He/she initiates and sustains the dragonshard conversion process and continually adjusts the output of the engine. The machinist can't steer the ship; he/she can only make it go forward. It takes someone with the Mark of Passage to operate the machine, though in theory, anybody trained in Arcana that has a high enough skill can operate the device via a skill challenge, but it's never been done before.

The four machinist's mates have the dull job of adjusting the energy fluctuation compensators. They don’t need to be trained in Arcana or have the Mark of Passage; anybody can do the job. The adjustments are necessary because at spelljamming speeds, slight fluctuations in ambient magical energy fields feel like turbulence in a modern jet to the eldritch machine’s processes.

You don’t know boring until you’ve spent all day adjusting energy fluctuation compensators. The monotony is worse than hunting for minerals in Mass Effect 2. Imagine hunching over a crystal ball and moving your hands around it all day long while trying to get the wavy patterns to look right and the noises to sound right.

The base speed of an aether drive is 20 million miles an hour. To go faster, the chief machinist may channel one daily or two encounter powers of equal level into the eldritch machine to boost speed by a number of million miles per hour equal to the channeled power’s level. Doing so degrades the dragonshards faster than normal, and they’ll likely fail at the earliest convenience of the DM. Powers may be channeled once per day and the speed boost lasts a day.

Right. I'm just sharing what I did for my SJ reboot in the hopes that it'll help get creative ideas flowing about what things we can do for the 4e conversion- assuming a conversion is the right direction. If you look at WoTC's The Plane Above, in a way they have rebooted spelljammer, or at least provided a foundation that could be built into spellljammer someday if they do a SJCG.

Making the minor helm a paragon tier item, for instance, that is awesome sauce. Not necessarily the direction I want for my campaign, but for a general conversion, that's brilliant as it lowers the entry bar. Adventuring on the Astral Sea is meant to be Paragon tier, so it totally makes sense.